UVB exposure associated with reduced risk of nearsightedness
Myopia is a complex trait influenced by numerous environmental and genetic factors and is becoming more common worldwide, most dramatically in urban Asia, but rises in prevalence have also been identified in the United States and Europe. This has major implications, both visually and financially, for the global burden from this potentially sight-threatening condition.
Teens and young adults who spend more time outdoors may be less likely to become nearsighted later in life than those who spend less time outdoors, a new study suggests.
People in the study who spent more time exposed to ultraviolet B (UVB) radiation, which the researchers calculated based on the participants' exposure to sunlight, between ages 14 and 39 were less likely to be nearsighted at 65 than those who spent less time exposed to UVB radiation, the researchers found.
In the study, the researchers looked at 371 people with nearsightedness and 2,797 people without nearsightedness who lived in various locations in Europe, including Norway, Estonia, France, Italy, Greece, Spain and the United Kingdom. The people in the study were 65 years old, on average.
The researchers found that an increase in UVB exposure at age 14 to 19 years and 20 to 39 years was associated with reduced odds of myopia; those in the highest tertile (group) of years of education had twice the odds of myopia. No independent associations between myopia and serum vitamin D3 concentrations or variants in genes associated with vitamin D metabolism were found. An unexpected finding was that the highest quintile (group) of plasma lutein concentrations was associated with reduced odds of myopia.
It is not clear exactly why UVB radiation or exposure to sunlight may be linked to a lower risk of nearsightedness, the researchers said. However, previous research suggested that sunlight might help stimulate the activation of certain cells in the eye, and may modulate a certain type of growth in the eye that is linked to nearsightedness, the researchers said.
Dr. Jules Winokur, an ophthalmologist at Lenox Hill Hospital in New York, who was not involved in the study, said that the study was interesting, but had certain limitations. For example, it relied on people's recollections of how much time they had spent outdoors many years ago, when they were teens, which may not be a reliable or accurate source of this type of information, he said.
More research is needed to assess the relationship between people's exposure to sunlight and their risk of nearsightedness, Winokur said.